Is it necessary to master or completely understand the run time complexity or "Analysis" of different algorithms for IOI?

I'm referring Introduction to Algorithms by CLRS,And i find it very hard to understand,the analysis part of the algorithms.Will it help me in the ZCO,INOI,IOI if I took the time to understand all the math and the complicated words they use to describe the analysis.Is it required for programming challenges,or should i just "know" the time complexity of the algorithsms like Insertion sort - O(n^2),Merge sort - O(n log n),etc?